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Suggestion audiometry for non-organic hearing loss (pseudohypoacusis) in children
International Journal of Pediatric Otorhinolaryngology 47 (1999) 11 – 21
Suggestion audiometry for non-organic hearing loss (pseudohypoacusis) in children Hiroshi Hosoi a,*, Yoshiaki Tsuta b, Kiyotaka Murata b, Harry Levitt c b
a Nara Medical Uni6ersity, Department of Otorhinolaryngology, 840 Shijocho, Kashihara, Nara 634 -8521, Japan Kinki Uni6ersity School of Medicine, Department of Otorhinolaryngology, 377 -2 Ohnohigashi, Osakasayama, Osaka 589, Japan c Speech and Hearing Sciences, City Uni6ersity of New York Graduate School, 33 West 42nd Street, New York 10036, USA
Received 8 January 1998; received in revised form 18 May 1998; accepted 20 May 1998
Abstract Pertaining to non-organic hearing loss in children, three goals should be attained: detection of this disease, determination of true hearing levels and information about the possible cause. Recently, objective tests have been used principally for children with non-organic hearing loss; however, these lack the simplicity and convenience of traditional audiometry. A new method, which is referred to as suggestion audiometry, since it is suggested to the patient that hearing will be improved as a result of the test procedure, was developed for the purpose of simultaneously achieving the above-stated three goals. The subjects were 20 patients aged 8 – 16 years suspected of demonstrating non-organic hearing loss and whose apparent hearing loss had been identified by school hearing examinations. Suggestion pure tone audiometry was useful for the detection of non-organic hearing loss and suggestion speech audiometry was valuable for the determination of true hearing levels. The subjects were classified into four groups according to the test results. We discuss causes of the disease based on the classification of the subjects obtained from this test procedure. © 1999 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Suggestion; Pure-tone audiometry; Speech audiometry; Non-organic hearing loss; Pseudohypoacusis; Children
1. Introduction When we see a child with poorer pure tone thresholds than would be expected based upon * Corresponding author. Tel.: + 81 744 29887; fax: + 81 744 24 6844; e-mail: [email protected]
conversational ability in the consultation room, we must determine whether the hearing loss is organic or non-organic. If the hearing loss is diagnosed as non-organic, two factors must be evaluated: the true hearing level and the cause of the non-organic hearing loss (NOHL). Regarding the latter, it must be determined whether misun-
0165-5876/99/$ - see front matter © 1999 Elsevier Science Ireland Ltd. All rights reserved. PII S0165-5876(98)00069-X
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derstanding or unfamiliarity with the test procedure is the cause of the poor test result or whether psychogenic factors or malingering underlie the poor pure tone test result. Regarding the detection of NOHL, several indicators of NOHL are evident in standard audiometric testing. These include poor test-retest reliability [1], ‘saucer-shaped audiogram’ [2,3], absence of a shadow curve (i.e. hearing by bone conduction from the opposite ear) in the case of a total unilateral loss, and inter-test discrepancy between the speech-reception threshold (SRT) and pure tone air conduction thresholds based on the audiometric speech frequency average (500 Hz, 1, and 2 kHz) [1,2,4–6]. Jerger and Herer [7] reported that patients with NOHL sometimes showed a type V pattern, i.e. the tracings for interrupted tones showed poorer hearing than those for continuous tones. There are also specialized tests for NOHL, such as the Doerfler – Stewart test [8], Lombard test, delayed auditory feedback [9], Stenger test [10], and other similar tests [11]. Concerning the determination of true pure tone thresholds, there are already a plethora of tests for NOHL. These can be classified into two groups: (i) special tests for NOHL; and (ii) objective tests, such as electric response audiometry (ERA). There are some special tests for NOHL which aim at estimation of true hearing thresholds, such as a modified Stenger test and a modified Doerfler – Stewart’s test [12]. However, some of these methods require special instruments or long testing periods. The Stenger test is restricted to cases with unilateral NOHL, although it is useful in determining the true hearing level [13]. These tests are relatively complicated for the subject and depend on subjective judgments by the subject, which can be highly variable. Objective tests, on the other hand, are less variable, and there is no danger of the subject not understanding the test. Thus, as Knight and Beagle [14] reported, many researchers consider ERA the primary tool for the diagnosis of NOHL. ERA, especially auditory brainstem response (ABR), is widely used for measuring true hearing thresholds in suspected cases of NOHL [15,16]. However, these tests do not use pure tone stimuli and do not provide a direct measure of the pure tone audiogram. ERA is an attractive option
in dealing with NOHL, but it lacks the simplicity and convenience of traditional audiometry. Recently, the clinical application of oto-acoustic emissions in evaluating NOHL has been reported [13,17]; however, it can examine only peripheral auditory function objectively. There have been several reports regarding the cause of NOHL in children. Hallewell et al. [18] reported a case with severe bilateral hearing loss who had normal hearing under hypnosis. Barr [19] analyzed the background of children with psychogenic hearing loss and consequently determined that they could not adapt themselves to the school environment. He also determined that the extra attention paid to the children because of the hearing difficulty had encouraged them, consciously or unconsciously, to feign a hearing loss. Lumio et al. [20] reported three cases of presumed psychogenic hearing loss due to family conflict. Some researchers regard NOHL in children as malingering [21], while others consider it a psychogenic disorder [20]. Three major aims should be achieved when considering NOHL in children: development of audiometry which can detect NOHL, determination of the true hearing level (i.e. true pure tone audiogram) and elucidation of possible causes. Regarding the detection and determination of true hearing levels, the problem can be solved for some of these patients by repeated testing. However, initially it cannot be known how many times the test must be repeated, and in cases that involve psychogenic factors, non-essential repeat tests should be avoided. Hence, we developed a new approach, which is referred to as suggestion audiometry, since it is suggested to the patient that hearing will be improved as a result of the test procedure. In this paper, we discuss the usefulness of this method in connection with detection of NOHL, determination of hearing levels and elucidation of causes.
2. Materials and methods
2.1. Information to the patients Whenever there was reason to suspect NOHL in
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in a child, we provided information about NOHL to the parents before performing any further testing. We then described the test procedures that could be performed, such as ABR, speech audiometry, Bekesy audiometry and suggestion audiometry, and how these tests should be interpreted. In particular, we explained suggestion audiometry in detail. We first outlined the purpose of suggestion audiometry, followed by a description of the technique itself, its effectiveness and its limitations. We also pointed out that the patient would be subject to some deception, at least initially. After explaining the overall plan for diagnosis of the hearing impairment, we asked the parents whether or not they agreed to the use of suggestion audiometry.
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out, the examiner tells the patient that hearing will improve using a hearing aid. First, pointing to the hearing aid, the examiner provides information about the device, describing it as an instrument that greatly improves hearing [Fig. 1(a)]. Second, the examinee is fitted with the hearing aid which is not turned on, and is without tubing or an ear tip, as shown in Fig. 1(b). Since tubing and an ear tip are excluded, an audiometric ear phone can be attached easily to the patient’s ear and pure tone audiometry can be performed in the usual way. Fig. 1(c) shows an examinee wearing an earphone and a hearing aid. Before the actual testing in the 20 study subjects, we confirmed using five normal hearing subjects that no threshold differences existed whether or not the hearing aid was being worn.
2.2. Subjects 2.4. Experimental procedure Subjects were 20 patients, aged 8 – 16 years whose apparent hearing losses had been identified by school hearing examinations and whose parents agreed to this test procedure. Bilateral impairment was seen in 12 cases, while eight cases involved unilateral impairment. All the subjects were tested using standard pure tone audiometry at frequencies of 125, 250, 500, 1000, 2000, 4000, and 8000 Hz after several practice trials. All the subjects had normal intelligence. Despite the high average hearing levels obtained using standard pure tone audiometry, all of the children could follow normal conversational speech without difficulty. The children also had normal ABR responses using tone pips as stimuli. The results of these tests indicate that all 20 subjects demonstrated NOHL.
2.3. Methodology of suggestion audiometry Suggestion audiometry can be performed using a standard audiometer and a typical behindthe-ear hearing aid. For suggestion speech audiometry, a tape deck is used with the audiometer. The basic procedure of suggestion audiometry is the same as that for standard audiometry. However, before the test is carried
Prior to administering suggestion pure tone audiometry, standard pure tone audiometry was performed, and is referred to as pre-suggestion pure tone audiometry. Next, suggestion audiometry was carried out on the same subjects who were then wearing a hearing aid. This procedure is referred to as mid-suggestion pure tone audiometry. Finally, after the hearing aids were removed from the subjects ears, which released them from the suggestion, standard pure tone audiometry was performed. This is called postsuggestion pure tone audiometry. Audiograms obtained from these three test conditions were compared. Suggestion SRT measurement was also performed, using the method of speech audiometry authorized by the Japan Audiological Society. SRT data were obtained from 12 of the 20 subjects, eight bilateral and four unilateral cases. The remaining eight subjects had normal SRTs even before suggestion, and it was considered unnecessary to perform suggestion speech audiometry on these subjects. Three measurements of SRT were obtained: pre-, mid- and post-suggestion. The method of suggestion was the same as for pure tone audiometry.
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Fig. 1. Instrumentation for suggestion audiometry. In section (a), an examiner shows the hearing aid to the patient, explaining that it will improve hearing. Section (b) shows how the hearing aid is fitted to the patient without tubing or an ear tip. Section (c) shows how an audiometric earphone can be fitted over the hearing aid, allowing for pure tone and speech audiometry to be performed in the usual way.
3. Results
3.1. A case report A 14-year-old girl was informed for the first time of a possible bilateral hearing impairment after a hearing screening test at her school. She came to our hospital for a more detailed examination. There was nothing unusual about her family history, her past medical history or her tympanic membrane. Although her pure tone average thresholds (PTA) for 500, 1000, and 2000 Hz were elevated (70 dBHL, right ear; 80 dBHL, left ear), she could understand speech at normal voice levels. Since NOHL was suspected, suggestion au-
diometry was performed. Fig. 2 shows pre-, midand post-suggestion pure tone audiometric data for this patient. Fig. 2(a) shows the data for the right ear, Fig. 2(b) for the left ear. The pre-suggestion PTAs were 70 dBHL, right ear and 78 dBHL, left ear. The mid-suggestion PTAs were improved substantially to 25 dBHL, right ear and 17 dBHL, left ear. After the hearing aid was removed, the post-suggestion PTAs worsened to 47 dBHL, right ear and 45 dBHL, left ear; i.e. to values midway between her pre- and midsuggestion PTAs. Suggestion speech audiometry was then performed. The pre-suggestion SRTs were 45 dBHL, right ear and 50 dBHL, left ear. The mid-sugges-
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tion SRTs improved to 20 dBHL, right ear and 15 dBHL, left ear. Post-suggestion SRTs were the same as the mid-suggestion SRTs, i.e. the SRTs did not worsen after removal of the suggestion.
Fig. 3. Mean audiograms for unilateral case. Mean hearing levels as a function of frequency are shown for the three experimental conditions (pre-, mid- and post-suggestion). Data have been averaged over the eight subjects with unilateral hearing loss. Vertical bars show the S.E.M.
3.2. Results for suggestion audiometry
Fig. 2. Pure tone audiograms for case study. Pre-, mid- and post-suggestion audiograms are shown for a 14-year-old girl whose hearing screening test at school showed a possible bilateral hearing impairment: (a) data for the right ear; (b) data for the left ear.
Figs. 3 and 4 show the average pure tone hearing levels for the seven test frequencies. Fig. 3 shows data for the eight unilateral cases. Fig. 4(a) and (b) show data for the better and worse ear, respectively, of the 12 bilateral cases. The vertical bars show the S.E.M. hearing level at each test frequency. A repeated-measures analysis of variance (repeated across subjects) was performed on each of the two sets of data (unilateral, bilateral). In addition, a subject-by-subject analysis was performed to determine if the subjects behaved identically or in different ways in response to the three experimental conditions (pre-, mid- and post-suggestion). The analysis of variance for the unilateral case consisted of three factors: experimental condition, test frequency and subjects. No significant effect was found for test frequency or the interaction between experimental condition and test frequency, i.e. there was no significant change in hearing level as a function of frequency, and this result was found to hold for each of the three conditions that were investigated. Test condition was found to be statistically significant (F–ratio= 6.9; df= 2, 14; P=0.008). Mean hearing levels for the pre-, mid- and post-suggestion con-
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ditions were 43.0, 27.7 and 39.6 dBHL, respectively. These means were averaged over subjects and test frequency. A similar analysis was performed on the SRT data. The results showed a small but significant effect for test condition (Fratio = 6.5; df= 2,6; P = 0.032). In this case, there was a significant drop from the pre-suggestion (mean SRT = 27.5 dBHL) to the mid-suggestion (mean SRT= 17.5 dBHL) condition, but there was no significant change from the latter condition to the post-suggestion condition (mean SRT= 20.0 dBHL). The analysis of variance for the bilateral cases involved four factors: experimental condition (pre-, mid- and post-suggestion), ear (poorer or better), test frequency (125, 250, 500, 1000, 2000,
Fig. 4. Mean audiograms for bilateral case. Mean hearing levels as a function of frequency are shown for the three experimental conditions (pre-, mid- and post-suggestion): (a) data for the poorer ear; (b) data for the better ear. Data have been averaged over the 12 subjects with bilateral hearing loss. Vertical bars show the S.E.M.
4000, and 8000 Hz) and subjects (9–20). As before, experimental condition was found to be significant (F-ratio= 19.5; df = 2, 22; P B 0.001). Mean hearing levels for the pre-, mid- and postsuggestion conditions were 49.8, 19.8 and 32.9 dBHL, respectively. Although test frequency did not show a significant effect, there was a significant interaction between test frequency and experimental condition (F-ratio=4.5; df= 12, 132; PB 0.001). The nature of this interaction is evident from Fig. 4(a) and (b), where the curves relating hearing level to frequency show a downward trend for the pre-suggestion condition, an upward trend for the mid-suggestion condition and neither an upward or downward trend for the post-suggestion condition, though there are some small tendencies, such as a negative slope from 1 to 2 kHz. As expected, there was a significant difference in average hearing level between the poorer and better ear (F-ratio= 5.2; df= 1,11; P= 0.041). The magnitude of the difference between the two ears was small (35.9 vs. 32.5 dBHL). Neither of the other two main factors, experimental condition or test frequency, showed a significant interaction with between-ear differences. An analysis of variance was also performed on the SRT data. The results showed a significant effect for experimental condition (F-ratio= 5.2; df= 2, 14; P= 0.020). The pre-suggestion average SRT was 20.3 dBHL, which dropped to 11.3 dBHL for the mid-suggestion condition and increased to 15.0 dBHL for the post-suggestion condition. The difference between the pre-suggestion and mid-suggestion mean SRTs was statistically significant (t= 2.3; df= 14; PB 0.05), but the difference between the mid-suggestion and post-suggestion mean SRTs was not. There was, as expected, a significant ear effect (F= 6.9; df= 1,7; P = 0.033). The mean SRT for the poorer ear was 17.3 dBHL compared to 13.8 dBHL for the better ear. There was also a small but significant interaction between experimental condition and ear, with the poorer ear showing the greater improvement when going from the pre-suggestion to mid-suggestion condition (10 vs. 8 dB improvement). The relative change in SRTs for the two ears was reversed, however, in going
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from the mid-suggestion to post-suggestion conditions, with the better ear showing a larger change in mean SRT than the poorer ear (5 vs. 2 dB). These mean differences are relatively small, but the interaction term in the analysis of variance was nevertheless statistically significant (F-ratio = 3.9; df= 2, 14; P= 0.045). In addition to the analyses of variance, a posthoc analysis was performed on the data for each subject to determine if there were differences among subjects as a function of experimental condition. Since there were three comparisons of interest (pre- vs. mid-suggestion; mid- vs. postsuggestion and post- vs. pre-suggestion) for each of 32 ears (12 bilateral, 8 unilateral), the significance level used was reduced to allow for the effect of multiple comparisons. In order to reach a significance level of 0.05 for 3× 32 = 96 comparisons, the significance level used was reduced to 0.05/96 = 0.00052. Since the comparisons were all within subjects, the within-subject S.E.M. hearing level averaged over test frequency was used. It was determined from the analysis of variance that the within-subject S.E. for a difference between two mean hearing levels was 2.9 dB and that a difference of 9.6 dB was statistically significant at the 0.00052 level. Of the 96 comparisons analyzed, 63 were found to be statistically significant using the above criterion. It was thus possible, using these comparisons, to classify the subjects into four groups:
3.2.1. Group 1, ‘Full return’ These subjects showed a significant improvement in hearing level in going from the pre- to mid-suggestion condition and a corresponding deterioration in hearing level going from the mid- to
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post-suggestion condition, with no significant difference between the pre- and post-suggestion conditions.
3.2.2. Group 2, ‘Partial return’ A significant improvement was noted in hearing level in going from the pre- to mid-suggestion condition and a significant deterioration in hearing level in going from the mid- to post-suggestion condition. The post-suggestion deterioration in hearing level, however, was significantly less than the mid-suggestion improvement; i.e. the apparent hearing loss at the termination of testing was significantly less than that obtained initially. 3.2.3. Group 3, ‘No return’ As in the previous two groups, these subjects showed a significant improvement in hearing level in going from the pre- to mid- suggestion condition, but no significant change in hearing level going from the mid- to post-suggestion condition. 3.2.4. Group 4, ‘No change’ The subjects in this category showed no significant change in hearing level in going from the preto mid- to post-suggestion conditions. The above categorization was performed initially for each ear of the bilateral subjects. It was found, however, that the subjects essentially fell within the same groups, whichever ear was used for purposes of categorization. Table 1 shows the breakdown of subjects by group. A summary of the criteria used in grouping the subjects is also included. A similar analysis was formed on the SRT data for each subject. In this case, 18 of the 20 showed no significant change in SRT for the three experi-
Table 1 Subject grouping Group
Full return Partial return No return No change
No. of subjects
5 6 5 4
Criteria used to form groups Pre-HL\Mid-HL
Mid-HLBPost-HL
* * *
* *
Post-HLBPre-HL
* *
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significant difference between the SRT and ABR threshold levels. Although the between-ear difference was numerically larger for the SRT data (3.7 vs. average difference of 1.9 dB for the ABR thresholds), this difference was not statistically significant.
4. Discussion
Fig. 5. Comparison between pure-tone average (PTA), speech reception threshold (SRT) and hearing level measured by means of auditory brainstem response (ABR). Mean hearing levels for three frequency (500, 1000, 2000 Hz) PTA are shown by the open bars. Mean SRTs are shown by the shaded bars, as are the mean hearing levels measured by ABR. Vertical bars show the between-subject S.D. for each type of measurement.
mental conditions. Although these subjects, individually, did not show a significant change in SRT, there was a small trend towards an improved SRT for the mid-suggestion condition which, if averaged over subjects, was statistically significant. In addition, two of the subjects (one bilateral, one unilateral) showed a relatively large improvement in SRT for the mid-suggestion condition. The SRTs were not only less susceptible to suggestion, they were also consistently lower (i.e. better), than the PTAs. Fig. 5 shows mean hearing levels and SRTs as a function of experimental condition (pre-, mid- or post-suggestion). The largest difference between the two measures occurs for the pre-suggestion condition. The difference is relatively small for the mid-suggestion condition and moderately large for the post-suggestion condition. The average ABR threshold for the same set of ears (i.e. those ears for which an SRT was obtained) is also shown. Although the average ABR threshold was slightly lower than the average SRT for the mid-suggestion condition, these two thresholds did not differ significantly. An analysis of variance on the ABR and mid-suggestion SRT data showed a significant ear effect (F-ratio= 8.0; df=1,7; P =0.025) but no
The results showed that the method of suggestion had a substantial effect on hearing levels as measured using traditional audiometric procedures. Only four of the 20 children participating in the study did not show a significant change in hearing level with suggestion. Of these, two had pre-suggestion hearing levels of 20 and 26 dB (poorer ear). These hearing levels are within normal range, as defined for screening purposes. It is likely that at the initial school hearing screening, these children may have shown hearing levels that just exceeded the screening threshold for identifying children requiring further evaluation at an ENT clinic. From the perspective of this study, these children had borderline abnormal hearing levels and may not have been appropriate candidates for the study. Therefore, of the children exhibiting pre-suggestion hearing levels indicative of a hearing loss, only two did not show a significant suggestion effect. The magnitude of the suggestion effect was relatively large for the tonal thresholds; the average change in hearing level with suggestion being 26.3 dB, with several subjects showing changes \ 60 dB. The technique using tonal stimuli is thus relatively sensitive in identifying children who demonstrate this effect. The SRT measurements, in contrast, were less sensitive to the effects of suggestion, with the average change in SRT being 9.6 dB. On the other hand, the mid-suggestion SRT provided a relatively accurate estimate of the true hearing level. The mid-suggestion SRT was only 3.5 dB higher, on average, than the ABR threshold. The difference between the two measurements for individual subjects ranged from −10 to + 15 dB. Our results, which could not be obtained by other test procedures, provide some useful insights regarding possible causes of NOHL in chil-
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dren. There are at least four such possible causes: (1) a condition similar to adult malingering; (2) psychogenic or other functional factors; (3) improper testing techniques, unfamiliarity with the testing procedures, or attention disorders; (4) hearing loss for pure tones with good hearing for speech. Malingering in adults is usually performed for purposes of personal gain (e.g. for evidence in a lawsuit). Malingering in children, however, is more likely to result from a need to attract attention [22]. A child malingering with strong intention may possibly continue to do so even after the hearing aid, which is associated with special attention, is removed; i.e. at the post-suggestion stage. The data, however, indicate that this probability did not happen. Post-suggestion hearing levels were always either equal to or lower than the pre-suggestion levels, indicating a consistent pattern linking these two hearing levels. Children who would continue to malinger would be very unlikely to remember their pre-suggestion hearing levels, in which case there should be a random association between pre- and post-suggestion hearing levels; i.e. at least a few of the post-suggestion hearing levels should have been poorer than the pre-suggestion hearing levels. Since two of five children in the ‘full return’ group and three of six children in the ‘partial return’ group showed psychogenic evidence, i.e. family conflict or conflict with school friends, during the counselling, one of the possible causes of the elevated hearing levels for children in these groups might be a psychogenic factor. However, the remaining six children in these groups showed no evidence of psychogenic factors, hence, an attention disorder might be a possible cause in these children. It is possible for a child with an attention deficit to improve performance briefly, such as when encouraged to pay special attention during the crucial mid-suggestion stage. A related attentional problem could account for those children in the ‘no change’ group who demonstrated a significant hearing deficit for tonal stimuli. These children may have difficulty in paying attention to abstract stimuli such as tones, but little difficulty in paying attention to biologically relevant signals such as speech.
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A possible cause of the observed hearing loss that must not be overlooked is that of unfamiliarity with the test procedure. A simple method of testing for this possibility is to repeat the test several times and examine the data for evidence of a learning effect. This, unfortunately, is a timeconsuming process. It is possible, in the experiment reported here, that children in the ‘no return’ group performed in this way as a result of greater familiarity with the test procedure on the second, mid-suggestion test. None of the children in the ‘no return’ group, however, showed a further significant improvement in hearing level when tested a third time at the post-suggestion stage. A further improvement in hearing level at the post-suggestion stage would have been strong evidence of a learning effect. Although improvements in hearing level beyond the mid-suggestion stage were not observed, the possibility cannot be ruled out that increased familiarity with the test procedure was a factor, contributing in part, to the improvements shown in going from the presuggestion to the mid-suggestion stage. In considering other methods for determining NOHL, some may think that objective tests are superior to this method. We acknowledge that it is natural for many otolaryngologists and audiologists to want to obtain the pure-tone audiogram and speech reception threshold after elimination of non-organic factors, although we do not deny the usefulness of objective tests. The ABR technique is used here as the standard against which other techniques for measuring hearing level are evaluated. Although the ABR technique provides reasonably accurate, objective measurements of hearing level, it is neither convenient nor is the necessary instrumentation available at all test facilities. The mid-suggestion SRT measurements in our study, on the other hand, were relatively accurate, in that between-subject variability for the mid-suggestion condition was low (S.E.M. for eight subjects =2.8 dB) and the average mid-suggestion SRT was not significantly different from the average ABR threshold. An important practical advantage of this technique is that only the most basic audiometric equipment is needed. The measurement of SRT also provides information on the subject’s ability to process speech, a matter of great importance in audiometric evaluation.
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It may be thought that our method requires long testing periods. However, pre-suggestion audiometry is standard audiometry which is routinely performed even when methods other than ours are used. Therefore, the only additional time consumed by our method is that for mid- and post-suggestion audiometries. The procedure itself is the same as standard pure-tone or speech audiometry, which does not require a lengthy period. Moreover, when the purpose of the test is limited to detection of NOHL and determination of true hearing levels, only mid-suggestion audiometry is sufficient. The experiment involved some deception initially; i.e. the child was only informed after the tests were completed that the hearing aid was not connected and that the differences in the measured thresholds were a result of their believing that the hearing aid was working. The parents were not the subjects to any deception, as explained earlier. The use of deception can be avoided entirely by means of an approach analogous to the use of placebos in conventional medical experiments. In this case, a working hearing aid is used but is not always switched on. It is switched on for certain frequencies and off for other frequencies. The subject is advised of this possibility, but is not told which threshold measurements will use a working hearing aid. When the hearing aid is switched on, the measured hearing level will be lowered by an amount equal to the gain of the hearing aid. For obvious reasons, a low gain hearing aid with a known frequency-gain characteristic is used. For the SRT measurements, the hearing aid should have a flat frequency response. This approach is a little more troublesome than that used in this study, but it does avoid the use of deception. Regarding the follow-up of these patients, we consulted a psychiatrist whose principal interest is psychogenic problems of children after audiological data have been obtained. After analyzing the characteristics of each child, she formulated a plan for each child as to how to explain the result of suggestive audiometry to the patient and an actual counselling plan. No problem was reported regarding the deceptive factor involved with this
procedure. Of interest would be results of longterm observation of these children; however, this issue is beyond the scope of the present paper. 5. Conclusions Suggestion audiometry was developed for the purpose of detecting NOHL in children and also for obtaining a more accurate estimate of true hearing levels using standard pure tone audiometry. The results of this experiment showed that suggestion tonal audiometry is a sensitive technique for detecting NOHL, although the tonal thresholds obtained using this technique were not always accurate estimates of the child’s true thresholds. Suggestion tonal audiometry should thus be regarded as a useful screening tool for detecting NOHL, and other procedures may need to be considered if suggestion tonal thresholds are abnormal in any way. Suggestion speech audiometry will provide useful additional information as well as a more accurate estimate of the true hearing level, but this technique alone should not be regarded as a sufficient indicator of normal organic function. It is important when screening for hearing loss to consider the possibility that an organic hearing loss may accompany a NOHL. When a normal audiogram is obtained using suggestion audiometry, we need not proceed further in the screening process, because this hearing impairment can be assumed to be non-organic. In contrast, when an audiogram obtained from suggestion audiometry is not close to a normal audiogram, additional tests are needed, including ABR testing, speech audiometry and impedance audiometry, in order to determine if a conductive and/or sensorineural hearing loss is present in addition to the NOHL. Acknowledgements Preparation of this paper was supported, in part, by the Rehabilitation Engineering Research Center on Hearing Enhancement and Assistive Devices, Award Number H133E30015 from the National Institute on Disability and Rehabilitation Research, US Department of Education.
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[12] F.N. Martin, R.R. Hawkins, A modification of the Doerfler – Stewart test for the detection of non-organic hearing loss, J. Audit. Res. 3 (1963) 147 – 150. [13] M. Baldwin, P. Watkin, The clinical application of otoacoustic emissions in paediatric audiological assessment, J. Laryngol. Otol. 106 (1992) 301 – 306. [14] J. Knight, H. Beagley, Non-organic hearing loss in children, Audiology 9 (1970) 142 – 143. [15] J.W. Sanders, B.B. Lazenby, Auditory brainstem response measurement in the assessment of pseudohypoacusis, Am. J. Otol. 4 (1983) 292 – 299. [16] M. Yoshida, A. Noguchi, T. Uemura, Functional hearing loss in children, Int. J. Pediatr. Otorhinolaryngol. 17 (1989) 287 – 295. [17] J.D. Durrant, R.K. Kesterson, D.B. Kamerer, Evaluation of the non-organic hearing loss suspect, Am. J. Otol. 18 (1997) 361 – 367. [18] J.D. Hallewell, C.P. Goetzinger, M.L. Allen, G.O. Proud, The use of hypnosis in audiologic assessment, Acta Otolaryngol. (Stockh.) 61 (1966) 205 – 208. [19] B. Barr, Psychogenic deafness in school children, Audiology 2 (1963) 125 – 128. [20] J.S. Lumio, T. Jauhiainen, K. Gelhar, Three cases of functional deafness in the same family, J. Laryngol. Otol. 83 (1969) 299 – 304. [21] H.A.T. Bailey Jr., F.N. Martin, Non-organic hearing loss-case report, Laryngoscope 71 (1961) 209 – 210. [22] P.A. Campanelli, Simulated hearing losses in school children following identification audiometry, J. Audit. Res. 3 (1963) 91 – 108.
References [1] I.M. Ventry, J.B. Chaiklin, The efficiency of audiometric measures used to identify functional hearing loss, J. Audit. Res. 5 (1965) 196–211. [2] L.G. Doerfler, Psychogenic deafness and its detection, Ann. Otol. Rhinol. Laryngol. 60 (1951) 1045–1048. [3] R. Carhart, Audiometry in diagnosis, Laryngoscope 68 (1958) 253 – 279. [4] R. Carhart, Speech audiometry in clinical evaluation, Acta Otolaryngol. (Stockh.) 41 (1952) 18–42. [5] I.M. Ventry, J.B Chaiklin, Evaluation of pure tone audiogram configurations used in identifying adults with functional hearing loss, J. Audit. Res. 5 (1965) 212–218. [6] N.D. Lehrer, S. Hirschenfang, M.H. Miller, S. Radpour, Non-organic hearing problems in adolescents, Laryngoscope 74 (1964) 64 –69. [7] J. Jerger, G. Herer, An unexpected dividend in Bekesy audiometry, J. Speech Hear. Disord. 26 (1961) 390–391. [8] L.G. Doerfler, K. Stewart, Malingering and psychogenic deafness, J. Speech Disord. 11 (1946) 181–186. [9] J.W. Black, The effect of delayed side-tone upon vocal rate and intensity, J. Speech Hear. Disord. 16 (1951) 56 – 60. [10] J.B. Chaiklin, I.M. Ventry, The efficiency of audiometric measurement used to identify functional hearing loss, J. Audit. Res. 5 (1965) 196–211. [11] G.J. Taylor, An experimental study of tests for the detection of auditory malingering, J. Speech Hear. Disord. 14 (1949) 119 – 130.
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Suggestion audiometry for non-organic hearing loss (pseudohypoacusis) in children Hiroshi Hosoi a,*, Yoshiaki Tsuta b, Kiyotaka Murata b, Harry Levitt c b
a Nara Medical Uni6ersity, Department of Otorhinolaryngology, 840 Shijocho, Kashihara, Nara 634 -8521, Japan Kinki Uni6ersity School of Medicine, Department of Otorhinolaryngology, 377 -2 Ohnohigashi, Osakasayama, Osaka 589, Japan c Speech and Hearing Sciences, City Uni6ersity of New York Graduate School, 33 West 42nd Street, New York 10036, USA
Received 8 January 1998; received in revised form 18 May 1998; accepted 20 May 1998
Abstract Pertaining to non-organic hearing loss in children, three goals should be attained: detection of this disease, determination of true hearing levels and information about the possible cause. Recently, objective tests have been used principally for children with non-organic hearing loss; however, these lack the simplicity and convenience of traditional audiometry. A new method, which is referred to as suggestion audiometry, since it is suggested to the patient that hearing will be improved as a result of the test procedure, was developed for the purpose of simultaneously achieving the above-stated three goals. The subjects were 20 patients aged 8 – 16 years suspected of demonstrating non-organic hearing loss and whose apparent hearing loss had been identified by school hearing examinations. Suggestion pure tone audiometry was useful for the detection of non-organic hearing loss and suggestion speech audiometry was valuable for the determination of true hearing levels. The subjects were classified into four groups according to the test results. We discuss causes of the disease based on the classification of the subjects obtained from this test procedure. © 1999 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Suggestion; Pure-tone audiometry; Speech audiometry; Non-organic hearing loss; Pseudohypoacusis; Children
1. Introduction When we see a child with poorer pure tone thresholds than would be expected based upon * Corresponding author. Tel.: + 81 744 29887; fax: + 81 744 24 6844; e-mail: [email protected]
conversational ability in the consultation room, we must determine whether the hearing loss is organic or non-organic. If the hearing loss is diagnosed as non-organic, two factors must be evaluated: the true hearing level and the cause of the non-organic hearing loss (NOHL). Regarding the latter, it must be determined whether misun-
0165-5876/99/$ - see front matter © 1999 Elsevier Science Ireland Ltd. All rights reserved. PII S0165-5876(98)00069-X
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derstanding or unfamiliarity with the test procedure is the cause of the poor test result or whether psychogenic factors or malingering underlie the poor pure tone test result. Regarding the detection of NOHL, several indicators of NOHL are evident in standard audiometric testing. These include poor test-retest reliability [1], ‘saucer-shaped audiogram’ [2,3], absence of a shadow curve (i.e. hearing by bone conduction from the opposite ear) in the case of a total unilateral loss, and inter-test discrepancy between the speech-reception threshold (SRT) and pure tone air conduction thresholds based on the audiometric speech frequency average (500 Hz, 1, and 2 kHz) [1,2,4–6]. Jerger and Herer [7] reported that patients with NOHL sometimes showed a type V pattern, i.e. the tracings for interrupted tones showed poorer hearing than those for continuous tones. There are also specialized tests for NOHL, such as the Doerfler – Stewart test [8], Lombard test, delayed auditory feedback [9], Stenger test [10], and other similar tests [11]. Concerning the determination of true pure tone thresholds, there are already a plethora of tests for NOHL. These can be classified into two groups: (i) special tests for NOHL; and (ii) objective tests, such as electric response audiometry (ERA). There are some special tests for NOHL which aim at estimation of true hearing thresholds, such as a modified Stenger test and a modified Doerfler – Stewart’s test [12]. However, some of these methods require special instruments or long testing periods. The Stenger test is restricted to cases with unilateral NOHL, although it is useful in determining the true hearing level [13]. These tests are relatively complicated for the subject and depend on subjective judgments by the subject, which can be highly variable. Objective tests, on the other hand, are less variable, and there is no danger of the subject not understanding the test. Thus, as Knight and Beagle [14] reported, many researchers consider ERA the primary tool for the diagnosis of NOHL. ERA, especially auditory brainstem response (ABR), is widely used for measuring true hearing thresholds in suspected cases of NOHL [15,16]. However, these tests do not use pure tone stimuli and do not provide a direct measure of the pure tone audiogram. ERA is an attractive option
in dealing with NOHL, but it lacks the simplicity and convenience of traditional audiometry. Recently, the clinical application of oto-acoustic emissions in evaluating NOHL has been reported [13,17]; however, it can examine only peripheral auditory function objectively. There have been several reports regarding the cause of NOHL in children. Hallewell et al. [18] reported a case with severe bilateral hearing loss who had normal hearing under hypnosis. Barr [19] analyzed the background of children with psychogenic hearing loss and consequently determined that they could not adapt themselves to the school environment. He also determined that the extra attention paid to the children because of the hearing difficulty had encouraged them, consciously or unconsciously, to feign a hearing loss. Lumio et al. [20] reported three cases of presumed psychogenic hearing loss due to family conflict. Some researchers regard NOHL in children as malingering [21], while others consider it a psychogenic disorder [20]. Three major aims should be achieved when considering NOHL in children: development of audiometry which can detect NOHL, determination of the true hearing level (i.e. true pure tone audiogram) and elucidation of possible causes. Regarding the detection and determination of true hearing levels, the problem can be solved for some of these patients by repeated testing. However, initially it cannot be known how many times the test must be repeated, and in cases that involve psychogenic factors, non-essential repeat tests should be avoided. Hence, we developed a new approach, which is referred to as suggestion audiometry, since it is suggested to the patient that hearing will be improved as a result of the test procedure. In this paper, we discuss the usefulness of this method in connection with detection of NOHL, determination of hearing levels and elucidation of causes.
2. Materials and methods
2.1. Information to the patients Whenever there was reason to suspect NOHL in
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in a child, we provided information about NOHL to the parents before performing any further testing. We then described the test procedures that could be performed, such as ABR, speech audiometry, Bekesy audiometry and suggestion audiometry, and how these tests should be interpreted. In particular, we explained suggestion audiometry in detail. We first outlined the purpose of suggestion audiometry, followed by a description of the technique itself, its effectiveness and its limitations. We also pointed out that the patient would be subject to some deception, at least initially. After explaining the overall plan for diagnosis of the hearing impairment, we asked the parents whether or not they agreed to the use of suggestion audiometry.
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out, the examiner tells the patient that hearing will improve using a hearing aid. First, pointing to the hearing aid, the examiner provides information about the device, describing it as an instrument that greatly improves hearing [Fig. 1(a)]. Second, the examinee is fitted with the hearing aid which is not turned on, and is without tubing or an ear tip, as shown in Fig. 1(b). Since tubing and an ear tip are excluded, an audiometric ear phone can be attached easily to the patient’s ear and pure tone audiometry can be performed in the usual way. Fig. 1(c) shows an examinee wearing an earphone and a hearing aid. Before the actual testing in the 20 study subjects, we confirmed using five normal hearing subjects that no threshold differences existed whether or not the hearing aid was being worn.
2.2. Subjects 2.4. Experimental procedure Subjects were 20 patients, aged 8 – 16 years whose apparent hearing losses had been identified by school hearing examinations and whose parents agreed to this test procedure. Bilateral impairment was seen in 12 cases, while eight cases involved unilateral impairment. All the subjects were tested using standard pure tone audiometry at frequencies of 125, 250, 500, 1000, 2000, 4000, and 8000 Hz after several practice trials. All the subjects had normal intelligence. Despite the high average hearing levels obtained using standard pure tone audiometry, all of the children could follow normal conversational speech without difficulty. The children also had normal ABR responses using tone pips as stimuli. The results of these tests indicate that all 20 subjects demonstrated NOHL.
2.3. Methodology of suggestion audiometry Suggestion audiometry can be performed using a standard audiometer and a typical behindthe-ear hearing aid. For suggestion speech audiometry, a tape deck is used with the audiometer. The basic procedure of suggestion audiometry is the same as that for standard audiometry. However, before the test is carried
Prior to administering suggestion pure tone audiometry, standard pure tone audiometry was performed, and is referred to as pre-suggestion pure tone audiometry. Next, suggestion audiometry was carried out on the same subjects who were then wearing a hearing aid. This procedure is referred to as mid-suggestion pure tone audiometry. Finally, after the hearing aids were removed from the subjects ears, which released them from the suggestion, standard pure tone audiometry was performed. This is called postsuggestion pure tone audiometry. Audiograms obtained from these three test conditions were compared. Suggestion SRT measurement was also performed, using the method of speech audiometry authorized by the Japan Audiological Society. SRT data were obtained from 12 of the 20 subjects, eight bilateral and four unilateral cases. The remaining eight subjects had normal SRTs even before suggestion, and it was considered unnecessary to perform suggestion speech audiometry on these subjects. Three measurements of SRT were obtained: pre-, mid- and post-suggestion. The method of suggestion was the same as for pure tone audiometry.
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Fig. 1. Instrumentation for suggestion audiometry. In section (a), an examiner shows the hearing aid to the patient, explaining that it will improve hearing. Section (b) shows how the hearing aid is fitted to the patient without tubing or an ear tip. Section (c) shows how an audiometric earphone can be fitted over the hearing aid, allowing for pure tone and speech audiometry to be performed in the usual way.
3. Results
3.1. A case report A 14-year-old girl was informed for the first time of a possible bilateral hearing impairment after a hearing screening test at her school. She came to our hospital for a more detailed examination. There was nothing unusual about her family history, her past medical history or her tympanic membrane. Although her pure tone average thresholds (PTA) for 500, 1000, and 2000 Hz were elevated (70 dBHL, right ear; 80 dBHL, left ear), she could understand speech at normal voice levels. Since NOHL was suspected, suggestion au-
diometry was performed. Fig. 2 shows pre-, midand post-suggestion pure tone audiometric data for this patient. Fig. 2(a) shows the data for the right ear, Fig. 2(b) for the left ear. The pre-suggestion PTAs were 70 dBHL, right ear and 78 dBHL, left ear. The mid-suggestion PTAs were improved substantially to 25 dBHL, right ear and 17 dBHL, left ear. After the hearing aid was removed, the post-suggestion PTAs worsened to 47 dBHL, right ear and 45 dBHL, left ear; i.e. to values midway between her pre- and midsuggestion PTAs. Suggestion speech audiometry was then performed. The pre-suggestion SRTs were 45 dBHL, right ear and 50 dBHL, left ear. The mid-sugges-
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tion SRTs improved to 20 dBHL, right ear and 15 dBHL, left ear. Post-suggestion SRTs were the same as the mid-suggestion SRTs, i.e. the SRTs did not worsen after removal of the suggestion.
Fig. 3. Mean audiograms for unilateral case. Mean hearing levels as a function of frequency are shown for the three experimental conditions (pre-, mid- and post-suggestion). Data have been averaged over the eight subjects with unilateral hearing loss. Vertical bars show the S.E.M.
3.2. Results for suggestion audiometry
Fig. 2. Pure tone audiograms for case study. Pre-, mid- and post-suggestion audiograms are shown for a 14-year-old girl whose hearing screening test at school showed a possible bilateral hearing impairment: (a) data for the right ear; (b) data for the left ear.
Figs. 3 and 4 show the average pure tone hearing levels for the seven test frequencies. Fig. 3 shows data for the eight unilateral cases. Fig. 4(a) and (b) show data for the better and worse ear, respectively, of the 12 bilateral cases. The vertical bars show the S.E.M. hearing level at each test frequency. A repeated-measures analysis of variance (repeated across subjects) was performed on each of the two sets of data (unilateral, bilateral). In addition, a subject-by-subject analysis was performed to determine if the subjects behaved identically or in different ways in response to the three experimental conditions (pre-, mid- and post-suggestion). The analysis of variance for the unilateral case consisted of three factors: experimental condition, test frequency and subjects. No significant effect was found for test frequency or the interaction between experimental condition and test frequency, i.e. there was no significant change in hearing level as a function of frequency, and this result was found to hold for each of the three conditions that were investigated. Test condition was found to be statistically significant (F–ratio= 6.9; df= 2, 14; P=0.008). Mean hearing levels for the pre-, mid- and post-suggestion con-
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ditions were 43.0, 27.7 and 39.6 dBHL, respectively. These means were averaged over subjects and test frequency. A similar analysis was performed on the SRT data. The results showed a small but significant effect for test condition (Fratio = 6.5; df= 2,6; P = 0.032). In this case, there was a significant drop from the pre-suggestion (mean SRT = 27.5 dBHL) to the mid-suggestion (mean SRT= 17.5 dBHL) condition, but there was no significant change from the latter condition to the post-suggestion condition (mean SRT= 20.0 dBHL). The analysis of variance for the bilateral cases involved four factors: experimental condition (pre-, mid- and post-suggestion), ear (poorer or better), test frequency (125, 250, 500, 1000, 2000,
Fig. 4. Mean audiograms for bilateral case. Mean hearing levels as a function of frequency are shown for the three experimental conditions (pre-, mid- and post-suggestion): (a) data for the poorer ear; (b) data for the better ear. Data have been averaged over the 12 subjects with bilateral hearing loss. Vertical bars show the S.E.M.
4000, and 8000 Hz) and subjects (9–20). As before, experimental condition was found to be significant (F-ratio= 19.5; df = 2, 22; P B 0.001). Mean hearing levels for the pre-, mid- and postsuggestion conditions were 49.8, 19.8 and 32.9 dBHL, respectively. Although test frequency did not show a significant effect, there was a significant interaction between test frequency and experimental condition (F-ratio=4.5; df= 12, 132; PB 0.001). The nature of this interaction is evident from Fig. 4(a) and (b), where the curves relating hearing level to frequency show a downward trend for the pre-suggestion condition, an upward trend for the mid-suggestion condition and neither an upward or downward trend for the post-suggestion condition, though there are some small tendencies, such as a negative slope from 1 to 2 kHz. As expected, there was a significant difference in average hearing level between the poorer and better ear (F-ratio= 5.2; df= 1,11; P= 0.041). The magnitude of the difference between the two ears was small (35.9 vs. 32.5 dBHL). Neither of the other two main factors, experimental condition or test frequency, showed a significant interaction with between-ear differences. An analysis of variance was also performed on the SRT data. The results showed a significant effect for experimental condition (F-ratio= 5.2; df= 2, 14; P= 0.020). The pre-suggestion average SRT was 20.3 dBHL, which dropped to 11.3 dBHL for the mid-suggestion condition and increased to 15.0 dBHL for the post-suggestion condition. The difference between the pre-suggestion and mid-suggestion mean SRTs was statistically significant (t= 2.3; df= 14; PB 0.05), but the difference between the mid-suggestion and post-suggestion mean SRTs was not. There was, as expected, a significant ear effect (F= 6.9; df= 1,7; P = 0.033). The mean SRT for the poorer ear was 17.3 dBHL compared to 13.8 dBHL for the better ear. There was also a small but significant interaction between experimental condition and ear, with the poorer ear showing the greater improvement when going from the pre-suggestion to mid-suggestion condition (10 vs. 8 dB improvement). The relative change in SRTs for the two ears was reversed, however, in going
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from the mid-suggestion to post-suggestion conditions, with the better ear showing a larger change in mean SRT than the poorer ear (5 vs. 2 dB). These mean differences are relatively small, but the interaction term in the analysis of variance was nevertheless statistically significant (F-ratio = 3.9; df= 2, 14; P= 0.045). In addition to the analyses of variance, a posthoc analysis was performed on the data for each subject to determine if there were differences among subjects as a function of experimental condition. Since there were three comparisons of interest (pre- vs. mid-suggestion; mid- vs. postsuggestion and post- vs. pre-suggestion) for each of 32 ears (12 bilateral, 8 unilateral), the significance level used was reduced to allow for the effect of multiple comparisons. In order to reach a significance level of 0.05 for 3× 32 = 96 comparisons, the significance level used was reduced to 0.05/96 = 0.00052. Since the comparisons were all within subjects, the within-subject S.E.M. hearing level averaged over test frequency was used. It was determined from the analysis of variance that the within-subject S.E. for a difference between two mean hearing levels was 2.9 dB and that a difference of 9.6 dB was statistically significant at the 0.00052 level. Of the 96 comparisons analyzed, 63 were found to be statistically significant using the above criterion. It was thus possible, using these comparisons, to classify the subjects into four groups:
3.2.1. Group 1, ‘Full return’ These subjects showed a significant improvement in hearing level in going from the pre- to mid-suggestion condition and a corresponding deterioration in hearing level going from the mid- to
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post-suggestion condition, with no significant difference between the pre- and post-suggestion conditions.
3.2.2. Group 2, ‘Partial return’ A significant improvement was noted in hearing level in going from the pre- to mid-suggestion condition and a significant deterioration in hearing level in going from the mid- to post-suggestion condition. The post-suggestion deterioration in hearing level, however, was significantly less than the mid-suggestion improvement; i.e. the apparent hearing loss at the termination of testing was significantly less than that obtained initially. 3.2.3. Group 3, ‘No return’ As in the previous two groups, these subjects showed a significant improvement in hearing level in going from the pre- to mid- suggestion condition, but no significant change in hearing level going from the mid- to post-suggestion condition. 3.2.4. Group 4, ‘No change’ The subjects in this category showed no significant change in hearing level in going from the preto mid- to post-suggestion conditions. The above categorization was performed initially for each ear of the bilateral subjects. It was found, however, that the subjects essentially fell within the same groups, whichever ear was used for purposes of categorization. Table 1 shows the breakdown of subjects by group. A summary of the criteria used in grouping the subjects is also included. A similar analysis was formed on the SRT data for each subject. In this case, 18 of the 20 showed no significant change in SRT for the three experi-
Table 1 Subject grouping Group
Full return Partial return No return No change
No. of subjects
5 6 5 4
Criteria used to form groups Pre-HL\Mid-HL
Mid-HLBPost-HL
* * *
* *
Post-HLBPre-HL
* *
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significant difference between the SRT and ABR threshold levels. Although the between-ear difference was numerically larger for the SRT data (3.7 vs. average difference of 1.9 dB for the ABR thresholds), this difference was not statistically significant.
4. Discussion
Fig. 5. Comparison between pure-tone average (PTA), speech reception threshold (SRT) and hearing level measured by means of auditory brainstem response (ABR). Mean hearing levels for three frequency (500, 1000, 2000 Hz) PTA are shown by the open bars. Mean SRTs are shown by the shaded bars, as are the mean hearing levels measured by ABR. Vertical bars show the between-subject S.D. for each type of measurement.
mental conditions. Although these subjects, individually, did not show a significant change in SRT, there was a small trend towards an improved SRT for the mid-suggestion condition which, if averaged over subjects, was statistically significant. In addition, two of the subjects (one bilateral, one unilateral) showed a relatively large improvement in SRT for the mid-suggestion condition. The SRTs were not only less susceptible to suggestion, they were also consistently lower (i.e. better), than the PTAs. Fig. 5 shows mean hearing levels and SRTs as a function of experimental condition (pre-, mid- or post-suggestion). The largest difference between the two measures occurs for the pre-suggestion condition. The difference is relatively small for the mid-suggestion condition and moderately large for the post-suggestion condition. The average ABR threshold for the same set of ears (i.e. those ears for which an SRT was obtained) is also shown. Although the average ABR threshold was slightly lower than the average SRT for the mid-suggestion condition, these two thresholds did not differ significantly. An analysis of variance on the ABR and mid-suggestion SRT data showed a significant ear effect (F-ratio= 8.0; df=1,7; P =0.025) but no
The results showed that the method of suggestion had a substantial effect on hearing levels as measured using traditional audiometric procedures. Only four of the 20 children participating in the study did not show a significant change in hearing level with suggestion. Of these, two had pre-suggestion hearing levels of 20 and 26 dB (poorer ear). These hearing levels are within normal range, as defined for screening purposes. It is likely that at the initial school hearing screening, these children may have shown hearing levels that just exceeded the screening threshold for identifying children requiring further evaluation at an ENT clinic. From the perspective of this study, these children had borderline abnormal hearing levels and may not have been appropriate candidates for the study. Therefore, of the children exhibiting pre-suggestion hearing levels indicative of a hearing loss, only two did not show a significant suggestion effect. The magnitude of the suggestion effect was relatively large for the tonal thresholds; the average change in hearing level with suggestion being 26.3 dB, with several subjects showing changes \ 60 dB. The technique using tonal stimuli is thus relatively sensitive in identifying children who demonstrate this effect. The SRT measurements, in contrast, were less sensitive to the effects of suggestion, with the average change in SRT being 9.6 dB. On the other hand, the mid-suggestion SRT provided a relatively accurate estimate of the true hearing level. The mid-suggestion SRT was only 3.5 dB higher, on average, than the ABR threshold. The difference between the two measurements for individual subjects ranged from −10 to + 15 dB. Our results, which could not be obtained by other test procedures, provide some useful insights regarding possible causes of NOHL in chil-
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dren. There are at least four such possible causes: (1) a condition similar to adult malingering; (2) psychogenic or other functional factors; (3) improper testing techniques, unfamiliarity with the testing procedures, or attention disorders; (4) hearing loss for pure tones with good hearing for speech. Malingering in adults is usually performed for purposes of personal gain (e.g. for evidence in a lawsuit). Malingering in children, however, is more likely to result from a need to attract attention [22]. A child malingering with strong intention may possibly continue to do so even after the hearing aid, which is associated with special attention, is removed; i.e. at the post-suggestion stage. The data, however, indicate that this probability did not happen. Post-suggestion hearing levels were always either equal to or lower than the pre-suggestion levels, indicating a consistent pattern linking these two hearing levels. Children who would continue to malinger would be very unlikely to remember their pre-suggestion hearing levels, in which case there should be a random association between pre- and post-suggestion hearing levels; i.e. at least a few of the post-suggestion hearing levels should have been poorer than the pre-suggestion hearing levels. Since two of five children in the ‘full return’ group and three of six children in the ‘partial return’ group showed psychogenic evidence, i.e. family conflict or conflict with school friends, during the counselling, one of the possible causes of the elevated hearing levels for children in these groups might be a psychogenic factor. However, the remaining six children in these groups showed no evidence of psychogenic factors, hence, an attention disorder might be a possible cause in these children. It is possible for a child with an attention deficit to improve performance briefly, such as when encouraged to pay special attention during the crucial mid-suggestion stage. A related attentional problem could account for those children in the ‘no change’ group who demonstrated a significant hearing deficit for tonal stimuli. These children may have difficulty in paying attention to abstract stimuli such as tones, but little difficulty in paying attention to biologically relevant signals such as speech.
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A possible cause of the observed hearing loss that must not be overlooked is that of unfamiliarity with the test procedure. A simple method of testing for this possibility is to repeat the test several times and examine the data for evidence of a learning effect. This, unfortunately, is a timeconsuming process. It is possible, in the experiment reported here, that children in the ‘no return’ group performed in this way as a result of greater familiarity with the test procedure on the second, mid-suggestion test. None of the children in the ‘no return’ group, however, showed a further significant improvement in hearing level when tested a third time at the post-suggestion stage. A further improvement in hearing level at the post-suggestion stage would have been strong evidence of a learning effect. Although improvements in hearing level beyond the mid-suggestion stage were not observed, the possibility cannot be ruled out that increased familiarity with the test procedure was a factor, contributing in part, to the improvements shown in going from the presuggestion to the mid-suggestion stage. In considering other methods for determining NOHL, some may think that objective tests are superior to this method. We acknowledge that it is natural for many otolaryngologists and audiologists to want to obtain the pure-tone audiogram and speech reception threshold after elimination of non-organic factors, although we do not deny the usefulness of objective tests. The ABR technique is used here as the standard against which other techniques for measuring hearing level are evaluated. Although the ABR technique provides reasonably accurate, objective measurements of hearing level, it is neither convenient nor is the necessary instrumentation available at all test facilities. The mid-suggestion SRT measurements in our study, on the other hand, were relatively accurate, in that between-subject variability for the mid-suggestion condition was low (S.E.M. for eight subjects =2.8 dB) and the average mid-suggestion SRT was not significantly different from the average ABR threshold. An important practical advantage of this technique is that only the most basic audiometric equipment is needed. The measurement of SRT also provides information on the subject’s ability to process speech, a matter of great importance in audiometric evaluation.
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It may be thought that our method requires long testing periods. However, pre-suggestion audiometry is standard audiometry which is routinely performed even when methods other than ours are used. Therefore, the only additional time consumed by our method is that for mid- and post-suggestion audiometries. The procedure itself is the same as standard pure-tone or speech audiometry, which does not require a lengthy period. Moreover, when the purpose of the test is limited to detection of NOHL and determination of true hearing levels, only mid-suggestion audiometry is sufficient. The experiment involved some deception initially; i.e. the child was only informed after the tests were completed that the hearing aid was not connected and that the differences in the measured thresholds were a result of their believing that the hearing aid was working. The parents were not the subjects to any deception, as explained earlier. The use of deception can be avoided entirely by means of an approach analogous to the use of placebos in conventional medical experiments. In this case, a working hearing aid is used but is not always switched on. It is switched on for certain frequencies and off for other frequencies. The subject is advised of this possibility, but is not told which threshold measurements will use a working hearing aid. When the hearing aid is switched on, the measured hearing level will be lowered by an amount equal to the gain of the hearing aid. For obvious reasons, a low gain hearing aid with a known frequency-gain characteristic is used. For the SRT measurements, the hearing aid should have a flat frequency response. This approach is a little more troublesome than that used in this study, but it does avoid the use of deception. Regarding the follow-up of these patients, we consulted a psychiatrist whose principal interest is psychogenic problems of children after audiological data have been obtained. After analyzing the characteristics of each child, she formulated a plan for each child as to how to explain the result of suggestive audiometry to the patient and an actual counselling plan. No problem was reported regarding the deceptive factor involved with this
procedure. Of interest would be results of longterm observation of these children; however, this issue is beyond the scope of the present paper. 5. Conclusions Suggestion audiometry was developed for the purpose of detecting NOHL in children and also for obtaining a more accurate estimate of true hearing levels using standard pure tone audiometry. The results of this experiment showed that suggestion tonal audiometry is a sensitive technique for detecting NOHL, although the tonal thresholds obtained using this technique were not always accurate estimates of the child’s true thresholds. Suggestion tonal audiometry should thus be regarded as a useful screening tool for detecting NOHL, and other procedures may need to be considered if suggestion tonal thresholds are abnormal in any way. Suggestion speech audiometry will provide useful additional information as well as a more accurate estimate of the true hearing level, but this technique alone should not be regarded as a sufficient indicator of normal organic function. It is important when screening for hearing loss to consider the possibility that an organic hearing loss may accompany a NOHL. When a normal audiogram is obtained using suggestion audiometry, we need not proceed further in the screening process, because this hearing impairment can be assumed to be non-organic. In contrast, when an audiogram obtained from suggestion audiometry is not close to a normal audiogram, additional tests are needed, including ABR testing, speech audiometry and impedance audiometry, in order to determine if a conductive and/or sensorineural hearing loss is present in addition to the NOHL. Acknowledgements Preparation of this paper was supported, in part, by the Rehabilitation Engineering Research Center on Hearing Enhancement and Assistive Devices, Award Number H133E30015 from the National Institute on Disability and Rehabilitation Research, US Department of Education.
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